docs: def flux(self, photon_energy, distance=1 * u.kpc, seed=None):
          """Differential flux at a given distance from the source from a single
          seed photon field
  
          Parameters
          ----------
          photon_energy : :class:`~astropy.units.Quantity` float or array
              Photon energy array.
  
          distance : :class:`~astropy.units.Quantity` float, optional
              Distance to the source. If set to 0, the intrinsic luminosity will
              be returned. Default is 1 kpc.
  
          seed : int, str or None
              Number or name of seed photon field for which the IC contribution
              is required. If set to None it will return the sum of all
              contributions (default).
          """
          model = super(InverseCompton, self).flux(
              photon_energy, distance=distance
          )
  
          if seed is not None:
              # Test seed argument
              if not isinstance(seed, int):
                  if seed not in self.seed_photon_fields:
                      raise ValueError(
                          "Provided seed photon field name is not in"
                          " the definition of the InverseCompton instance"
                      )
                  else:
                      seed = list(self.seed_photon_fields.keys()).index(seed)
              elif seed > len(self.seed_photon_fields):
                  raise ValueError(
                      "Provided seed photon field number is larger"
                      " than the number of seed photon fields defined in the"
                      " InverseCompton instance"
                  )
  
              if distance != 0:
                  distance = validate_scalar(
                      "distance", distance, physical_type="length"
                  )
                  dfac = 4 * np.pi * distance.to("cm") ** 2
                  out_unit = "1/(s cm2 eV)"
              else:
                  dfac = 1
                  out_unit = "1/(s eV)"
  
              model = (self.specic[seed] / dfac).to(out_unit)
  
          return model